In general, nitride single crystal semiconductor thin film deposition is widely used
for forming a light-emitting diodes (LED) or a laser diodes. In order to form nitride single crystal semiconductors on a substrate it is generally necessary to maintain the substrate at a high temperature.
Conventional thin film processes require temperatures above 1,000° C. for crystal growth. The application area of single crystals that are made at such a high temperature is very limited.
Typical technologies used to form conventional nitride semiconductor crystals include MOCVD (Metal Organic CVD) and MBE (Molecular Beam Epitaxy). To obtain a nitride semiconductor thin film using these methods, the substrate should be maintained at a temperature between 1,050 and 1,100° C. Accordingly, deterioration of the substrate on which nitride semiconductor thin films are formed, for example due to thermal expansion of the sapphire substrates, or deformation of the substrate itself, can be a problem. Furthermore, the difference in lattice constant and coefficient of thermal expansion between the nitride semiconductor thin film formed on the substrate and the substrate can damage a thin film, which can be a problem.
Additionally, as an example of making a light emitting device, an n-type GaN layer,
InGaN active layer and a p-type GaN layer can be formed on top of a sapphire substrate. Impurities such as Mg and Si should be doped on top of the single GaN layer to form the N-type GaN and p-type GaN layers. In this case, if the heating temperature of the substrate is above 1,000° C. the diffusion of the doping impurity atoms is activated. For example, Mg doping atoms used to form the p-type GaN layer may spread into the multi-quantum well, the active layer of an LED, so that the emission characteristics of the light-emitting device is impaired. This may happen in the n-type GaN layer as well. Therefore, the emission characteristics of the light-emitting device will be ultimately degraded.
Patent No. 10-0251035 of the Republic of Korea suggests a method to make a single
crystal thin film using a neutral particle beam after an amorphous or polycrystalline thin film is made on the substrate using plasma CVD as described above.
However, the method disclosed in the publication above requires in advance the manufacture of amorphous or polycrystalline thin films by the plasma CVD method in order to obtain the desired single crystal thin films. Also, since reflectors of various structures should be provided in order to investigate the predetermined angle of the neutral particle beam for the purification of the films, a lot of effort must go into the production process and complex production equipment is required, which then increases the production costs of the semiconductor light-emitting devices leading to a lower LED supply or decreased marketability.